New Zealand has remained free from many exotic diseases and disease vectors (carriers). It is seen as important that effective Bio-security procedures are in put in place, and maintained, to enhance our natural barrier of isolation.
It is also seen that Bio-security activities undertaken by public health services can help to reduce the adverse health effects and to optimise the positive health effects of the global environment. Other agencies are also involved and these include the Ministry of Agriculture and Forestry, Ministry of Fisheries, Department of Conservation, Local Government, Industry, and the general public.
The Bio-security Act 1993 (section 2 (1)) has the provision to categorise certain organisms as ‘unwanted organisms of human health significance’. To date mosquitoes are the only organisms so defined.
Port Surveillance – Exotic Mosquitoes
The Port of Napier is an international seaport. Of the overseas vessels that come to it each year Napier is the first New Zealand Port for around 115 of them.
With the co-operation of the Port of Napier, the Hawke’s Bay District Health Board’s - Public Health Unit conducts mosquito surveillance operations at the port with 7 traps set within the port perimeter and 4 outside.
The traps are of the Ovitrap type, which consists of a container, generally blackened, filled with water and a porous paddle added. The trap is designed to offer a site for mosquitoes to oviposit (lay eggs). The eggs hatch as larvae, which are then collected, before they can complete their life cycle, and identified. The traps are visited, on a weekly basis during summer and a fortnightly basis during winter.
New Zealand has 16 species of mosquitoes, 4 of which are exotic (not native). Some of these species have very specific larval habitat – for example a species called Ochlerotatus chathamicus. This mosquito has only been found on the Chatham Islands and although it has not been extensively studied its larval habitat appears to be saline coastal rock pools.
The mosquito life cycle has 4 distinct stages – egg, larva, pupa, adult.
Eggs depending on the species, the eggs are laid either on the water surface, or just above the water surface (flood species). Some species breed in artificial containers, such as used tyres, roof guttering, etc. Others in natural habitat, such as swamps, drains etc. While some can breed in both artificial and natural habitats.
Larva swim and feed in water. They have 4 growth stages known as instars. They swim to the surface to breath through their breathing siphon.
Pupa is a resting stage. Pupa does not feed.
Adult male mosquitoes emerge from the pupa approximately a day before the female. They remain close to the breeding site to mate with females after they have emerged to the adult stage. Males live for only a matter of days, but the female lives longer than this. Most don’t live for more than 10-14 days but if environmental conditions are good a few may live longer. Males feed only on nectar and plant juices, but the female also needs a blood meal to obtain the necessary protein to produce eggs. Each species has preferences as to which animal(s) it obtains this blood meal from.
Exotic mosquitoes are those that are not native to New Zealand. Our natural barrier of distance can no longer be relied upon for protection. New Zealand has close relationships to areas of the world where disease carrying mosquitoes are common. Australia alone has over 200 different varieties of mosquito.
New Zealand has been free of any mosquito borne, human diseases. As a consequence the population have not been exposed to any great degree to arboviruses (diseases carried by a mosquito). It is considered that this makes the general population at risk to an epidemic. This risk is increased further due to the lack of knowledge about arboviruses, their effects and how to minimize the risks of being infected.
Mosquitoes at Home
Your place or mine?
Mosquitoes don’t care. They like to live and breed in standing water – any kind, anywhere, and in some very surprising places.
What you can do to stop them
Make them feel unwelcome. The best way to get rid of them is to stop them from breeding. A simple way to do this is by getting rid of things that hold water.
Avoid being bitten
Adult mosquitoes do not normally travel far from their breeding site. Most travel no further than 100 metres although some species are know to travel further. Some for many kilometres.
Most species are often active at dawn, around the late afternoon and just after dark, although some we have in New Zealand will also bite during the day
Collecting an Adult Sample
Please treat the sample with care. Harsh treatment will possibly damage the specimen to the extent of making identification difficult.
Health Protection Officer
Public Health Unit
Napier Health Centre
1st Floor, 76 Wellesley Road, Napier.
P O Box 447, Napier
Telephone: (06) 834-1815
Facsimile: (06) 834-1816